Fill level measuring devices often use antennas to bundle electromagnetic rays and to specify a direction of propagation of the electromagnetic rays, which are transmitted in the direction of a filling material. The reflections of the electromagnetic rays on the surface of a filling material are utilised to determine a fill level or the height of a bulk material. A filling material can thus be a material which is put into a container or a material that lies on an open space as a bulk material. Since the antennas are often implemented as horn antennas and are also frequently used in dirty environments, covers are used for the horn antennas in order to prevent dirt particles from getting inside the horn antenna. In addition to the protective effect against penetrating particles, the covers can also be used for beam formation, especially if they are manufactured from plastics material and have a suitable lens shape.
A dielectric lens is known from printed publication GB 1 410 699 and is suitable for bundling radio radiation.
Printed publication EP 2 515 376 A1 relates to an antenna cover for a fill level measuring device.
On account of the different thicknesses of a lens, however, production by injection moulding is difficult and lenses are therefore produced as turned parts.